The present invention pertains to the art of fluid separation. It is applicable to the separation of lighter liquids, such as oil, and heavier liquids, such as water. The invention finds particular application in the automatic removal and decantation of the contents of a layer of oil floating upon water contained in an enclosed basin and will be described with particular reference thereto. However, it is to be appreciated that the invention has other applications including the separation of various heavier and lighter fluids including foam, froth, gasoline, grease, emulsions, suspended particulates, floc, and the like from water, acids, alkali solutions, and the like.
Commonly oil enters process and waste water streams almost continuously, but in small amounts. The small, continuous flow causes problems with processes and with equipment if not removed. Usually a stilling basin is provided where the oil and water stagnate sufficiently for the oil to float to the surface.
Heretofore, various systems were developed for separating the oil and water. In one technique, a wier was disposed adjacent a downstream end of the basin which retained the oil while allowing the water to pass thereunder into a public stream. Periodically, the floating oil was removed by permitting it to flow over the weir to a drain. With the advent of pollution laws, the drain was connected with a tank from which the oil could be recovered.
One of the problems with this technique was that an attendant was required to monitor the oil level in the basin and control the overflow of the wier. The attendant had to position the wier overflow to fill the decanting tank. Once the tank was filled, the attendant stopped the flow into the tank and waited for the oil and water therein to separate or decant. After the oil and water separated, the attendant pumped the water from the bottom of the tank back into the basin and pumped the oil to a storage tank.
As the layer of oil in the basin became thinner, this technique became increasingly more labor intensive. Trying to maintain the basin free of a thin surface layer of oil was prohibitively expensive. Although attempts were made to automate the process, maintenance on the automated equipment was very expensive and the automated processes unsatisfactory.
As a cheaper solution, many operators permitted the oil to accumulate in the basin over long periods, e.g., months or years. As is to be appreciated, evaporation of low boiling fractions of the oil caused hydrocarbon contamination and an explosion hazard. Further, as the more volatile fractions evaporated, the specific gravity and viscosity of the oil increased. If left long enough, it reached neutral bouyancy with the water and passed under the baffle into the public stream or the lake. With the passage of tighter antipollution laws, these practices became not only unsatisfactory but also illegal.
Others have suggested devices that automatically and continuously remove and decant floating oil from basins. However, these devices require that operating conditions be maintained within very narrowly prescribed limits. One example of these continuous and automatic devices is a selective adhesion-type oil skimmer equipped with an automatic continuous decanter for removal of modest flows of relatively viscous oils.
Others have recognized that a vortex separates a mixture of lighter and heavier fluids. The lighter components collect toward the center of the vortex and the heavier components remain around the periphery. This technique has been used for separating a lighter liquid, such as an oil slick, from a heavier liquid, such as water. As shown for example in U.S. Pat. No. 3,635,342 to Mourlon or U.S. Pat. No. 4,142,972 to Nebeker, the vortex systems generally include an impeller, water jet, or the like, for creating a vortex in the water. The vortex forms a well in which a pool of oil collects. A pump is provided for removing oil which has accummulated in the vortex pool.
The prior art vortex separators have various drawbacks. Each requires a mechanical vortex creation means, such as an impellor.
The present invention contemplates a new and improved vortex separator which overcomes the above-referenced problems and others.